Data Storage System and Control Apparatus with a Switch Unit Connected to a Plurality of First Channel Adapter and Modules Wherein Mirroring Is Performed

1. A data storage system comprising: a plurality of memory devices for storing data; a plurality of control modules which accesses the 5 memory devices according to access instructions from a mainframe unit and an open system unit; a plurality first channel adapter which performs interface control to the mainframe unit; and a switch unit connected to the plurality of first channel adapter and the plurality of control modules, and for selectively switching the connection between the plurality of first channel adapter and the plurality of control modules, wherein each said control module comprises: a cache memory which stores a portion of data stored in the memory devices; a second channel adaptor which performs interface control to the open system unit; a disk adapter for performing interface control to the plurality of memory devices; and a control unit which controls the cache memory in response to the accesses, and accesses the memory devices via the disk adapter, and wherein, said first channel adapter, in response to a write access from the mainframe unit, accesses in parallel both one said control module taking charge of the write data to be the target of the write access, and another said control module having mirror data of the control module in charge through said switch unit, so as to perform mirroring.

2. The data storage system according to claim 1 , wherein the control module in charge decides whether a target write data block is existent in the cache memory of the control module, and when deciding a write miss that the target write data does not exist in the cache memory, both the control module in charge and the another control module access the memory device storing the target data block, and read the target data block.

3. The data storage system according to claim 1 , wherein the first channel adapter connects to the mainframe unit from the start of access to the end of access according to the protocol of the mainframe unit, and wherein the second channel adapter disconnects the connection to the open system unit on receiving the access from the open system unit, according to the protocol of the open system unit.

4. The data storage system according to claim 1 , further comprising: a plurality of other switch units provided between the plurality of control modules and the plurality of memory devices, and selectively switching between the disk adapter of each control module and the plurality of memory devices, wherein the plurality of control modules and the plurality of other switch units are connected by a back panel.

5. The data storage system according to claim 4 , wherein the control module connects the control unit to the first channel adapter through a high-speed serial bus of low latency, and the second channel adapter is connected to the plurality of other switch units through serial buses by the back panel.

6. The data storage system according to claim 5 , wherein each control module and the other switch units are connected by the back panel, and the other switch units and the plurality of memory devices are connected through cables.

7. The data storage system according to claim 4 , wherein each control module and the switch units are connected by the back panel, and the switch units and the first channel adapter are connected by the back panel.

8. The data storage system according to claim 1 , wherein the control module connects the control unit to the second channel adapter through a high-speed serial bus of low latency.

9. The data storage system according to claim 1 , wherein the control unit in each control module decides whether the data access from the open system unit through the connected second channel adapter is targeted to the data of which the control unit takes in charge, and when the data access is not targeted to the data of which the control unit takes in charge, the control unit requests the other control unit taking charge of the data to access the data requested from the open system unit, via the switch unit.

10. A data storage control apparatus comprising: a plurality of control modules which accesses a plurality of memory devices for storing data according to access instructions from a mainframe unit and an open system unit; a plurality of first channel adapter which performs interface control to the mainframe unit; and a switch unit connected to the first channel adapter and the plurality of control modules, and for selectively switching the connection between the plurality of first channel adapter and the plurality of control modules, wherein each control module comprises a cache memory which stores a portion of data stored in the memory devices; a second channel adapter which performs interface control to the open system unit; a disk adapter for performing interface control to the plurality of memory devices; and a control unit which controls the cache memory in response to the accesses, and accesses the memory devices via the disk adapter, wherein, said first channel adapter, in response to a write access from the mainframe unit, accesses in parallel both one said control module taking charge of the write data to be the target of the write access, and another said control module having mirror data of the control module in charge through said switch unit, so as to perform mirroring.

11. The data storage control unit according to claim 10 , wherein the control module in charge decides whether a target write data block is existent in the cache memory of the control module, and when deciding a write miss that does not exist the target write data in the cache memory, both the control module in charge and the another control module access the memory device storing the target data block, so as to read the target data block.

12. The data storage control apparatus according to claim 10 , wherein the first channel adapter connects to the mainframe unit from the start of access to the end of access according to the protocol of the mainframe unit, and wherein the second channel adapter disconnects the connection to the open system unit on receiving the access from the open system unit, according to the protocol of the open system unit.

13. The data storage control apparatus according to claim 10 , further comprising: a plurality of other switch units provided between the plurality of control modules and the plurality of memory devices, for selectively switching between the disk adapter of each control module and the plurality of memory devices, wherein the plurality of control modules and the plurality of other switch units are connected by a back panel.

14. The data storage control apparatus according to claim 13 , wherein the control module connects the control unit to the second channel adapter through a high-speed serial bus of low latency, and the second channel adapter is connected to the plurality of other switch units through serial buses by the back panel.

15. The data storage control apparatus according to claim 14 , wherein each control module and the other switch units are connected by the back panel, and the other switch units and the plurality of memory devices are connected through cables.

16. The data storage control apparatus according to claim 13 , wherein each control module and the switch units are connected by the back panel, and the switch units and the first channel adaptor are connected by the back panel.

17. The data storage control apparatus according to claim 10 , wherein the control module connects the control unit to the second channel adapter through a high-speed serial bus of low latency.

18. The data storage control apparatus according to claim 10 , wherein the control unit in each control module decides whether the data access from the open system unit through the connected second channel adapter is targeted to the data of which the control unit takes in charge, and when the data access is not targeted to the data of which the control unit takes in charge, the control unit requests the other control unit taking charge of the data to access the data requested from the open system unit, via the switch unit.